1. Field of the Invention
The present invention relates to a canister for adsorbing fuel vapor vaporized in a fuel tank and a filter for the canister.
2. Description of Related Art
A fuel vapor processing apparatus is provided in a vehicle, which has an internal combustion engine (hereinafter, referred to as an engine), to remove fuel vapor generated in a fuel tank or in the engine and thereby to reduce the fuel vapor released into the atmosphere. In the fuel vapor processing apparatus, a canister is arranged in a passage, which connects between the fuel tank and an intake pipe of the engine, to adsorb and remove fuel vapor vaporized in the fuel tank and the engine. The air, which contains fuel vapor vaporized in the fuel tank and the engine, is released into the atmosphere through the canister. Thus, the fuel vapor is removed from the air, so that the amount of fuel vapor released into the atmosphere is reduced. At the time of operating the engine, the atmospheric air is introduced into the canister. Thus, the fuel vapor adsorbed by the canister is desorbed from the canister and is supplied into the intake pipe together with the atmospheric air introduced into the canister.
As described above, the atmospheric air is introduced into the canister. Thus, a filter for filtering foreign particles is arranged in an atmospheric air passage, which connects between the canister and the atmosphere (see Japanese Unexamined Patent Publication Number 7-217506).
However, although the fuel vapor is mostly removed from the air when it passes through the canister, the fuel vapor cannot be completely removed from the air. This is due to the fact that the fuel vapor contains components, which are difficult to remove by the adsorbent material of the canister. Particularly lately, it has been demanded to further reduce the amount of fuel vapor released from the fuel tank into the atmosphere. Thus, it is required to reduce the amount of vapor fuel, which passes through the canister.